The invention relates to magnetic disk files and more particularly to carriages having magnetic heads for sensing a servo track on a magnetic disk and for reading from and writing on associated data tracks, the servo track and data tracks being provided on the same recording surface of the disk.
Some prior track following concepts have incorporated a single servo read head to follow a prewritten servo track on a recording disk. One such file uses a servo head on the bottom of a disk to access and locate two data heads on the top surface of the disk. In such a system, 66% of the total used disk surface is used for data. This efficiency can be enhanced by stacking many disks and using only one servo surface, and this approach is employed on large files. Unfortunately, the ultimate track density is limited by the many mechanical tolerances that build up from head to head and disk to disk. This limitation is particularly acute when the disks are made of thin flexible media which has poor dimensional stability. Such a type of media dictates for reasonably high track densities that the servo information must be included on the same disk as the data; and, in most cases, it must be on the same side of the disk as the data.
Recent technology efforts using thin film head arrays utilize multitrack heads to do the track following function in addition to the reading and writing functions. Such an arrange may include six read only servo heads used to track follow and a separate read/write head used for data transfer. One servo track is located at one end of a series of data tracks (such as six data tracks), and an array of six servo heads are aligned consecutively with the servo track in order to bring the single read/write head in alignment with the six data tracks. This approach, therefore, yields six data tracks per servo track or 6/7=85.7% usage of the disk for data storage. This approach also results in a rather complex head assembly that must be as wide as the number of tracks in a band (seven tracks in this case). There are also cross talk exposures on the servo heads closest to the read/write head.